I know what you guys are thinking but many people have asked me how to do that. So i thought i should make a post about it.
So here we go.
Step 1: Obviously you have to install whatsapp on your dear smartphone to get through with the steps.
Step 2: Now open Whatsapp and goto settings tab. Then click on 'Notifications' button which should be right below 'Chat Settings' button.
Step 3: Then under 'New Messages' set a tone of your choice and do the same for 'Group Message' and set In-App Vibrate and In-App Sounds to be 'On'.
Step 4: Now, if you want to set it on vibrate either set your phone to vibration mode or turn In-App Sounds off. And if you want it to ring then switch In-App souds ON and turn your phone too to ringing.
I hope it was helpful to those it concerned :)